Skip the auto shop - Our mechanics make house calls

P0159 OBD-II Trouble Code: Oxygen Sensor (Bank 2 Sensor 2)

Check Engine Light

P0159 trouble code definition

Oxygen Sensor (O2) Circuit Slow Response (Bank 2 Sensor 2)

What the P0159 code means

Code P0159 is a powertrain code that indicates a specific sensor in the exhaust system (bank 2 sensor 2) is not performing as it should. When an oxygen sensor modulates slowly, it is an indication it is bad. This sensor monitors the catalyst efficiency for emissions purposes.

What causes the P0159 code?

This code is set if the oxygen sensor modulates slowly. It should fluctuate between 800mv and 250mv 16 times in a twenty second period. If the sensor does not perform to this standard, it is considered to be bad. Usually due to age or contamination.

Exhaust leaks will set this code as well. Contrary to popular belief, an exhaust leak will suck in oxygen diluting the exhaust flow that will simulate the conditions the computer interprets as a bad oxygen sensor.

This is a four wire sensor with two circuits. If either of these circuits has a short or high resistance, this code could be set as these conditions will affect the oxygen sensor’s ability to perform properly.

What are the symptoms of the P0159 code?

A Check Engine Light. This sensor is mainly for emissions purpose and does not have a significant effect on the performance of the vehicle.

This is a downstream oxygen sensor, meaning it is after the catalytic converter. The computer utilizes downstream oxygen sensors to monitor catalyst efficiency and upstream oxygen sensors to calculate air fuel mixture.

How does a mechanic diagnose the P0159 code?

Technical Service Bulletins (TSB’s) should be checked for problems specific to individual year make and model vehicles.

The computer sets this code after performing some very specific tests. For this reason, a technician having scanned the vehicle and finding this code will likely confirm there aren’t any exhaust leaks before replacing the indicated sensor (bank 2 sensor 2).

If more extensive tests should be necessary, there are variety of methods to do so. A technician can tap directly into the oxygen sensors circuit and observe its function with an oscilloscope. This is usually performed while introducing propane into the intake or creating a vacuum leak and observing how the oxygen sensor reacts to the change in conditions. These tests are often done in conjunction with a test drive.

Resistance tests can be taken with the oxygen sensors connector unplugged from the vehicle's electrical harness. At times, this is done while applying heat to the sensor simulating conditions the sensor would experience when installed in the exhaust system.

Common mistakes when diagnosing the P0159 code

Failing to spot other problems, such as exhaust leaks, vacuum leaks, or misfires are not uncommon. Sometimes other problems can be subtle and easy to miss.

Downstream O2 sensors (O2 sensors after the catalytic converter) exist to make sure the vehicle meets the EPA’s tailpipe emissions standards. Not only does this O2 sensor test the catalyst efficiency, but tests are performed to test the effectiveness of the sensor itself.

The stringent nature of these tests require all other systems to be operating correctly or the results may not be accurate. For this reason, most other codes and symptoms should be addressed first.

How serious is the P0159 code?

This code has a low impact on the daily driving of the vehicle. This is not a system that will make a tow truck necessary.

The seriousness of global warming is what has prompted the EPA and auto manufactures to implement systems such as this.

What repairs can fix the P0159 code?

  • The most common repair is the replacement of the indicated oxygen sensor (bank 2 sensor 2).

  • Exhaust leaks must be repaired before any oxygen sensor is replaced.

  • It is not uncommon to find damaged wiring in the oxygen sensor circuit that would need to be repaired. These circuits are shielded and require extra attention when fixing them.

Additional comments for consideration regarding the P0159 code.

  • Bank 1 is the set of cylinders with number one cylinder in it.

  • Bank 2 is the set of cylinders that does not have number one cylinder.

  • Sensor 1 is the sensor before the catalytic converter which the computer uses to make fuel ratio calculations.

  • Sensor 2 is the sensor that comes after the catalytic converter and is mainly used for onboard emissions testing.

The following conditions must be met for your car to test the health of the bank 2 sensor 2 O2 sensor. This fault detection method may vary between manufacturers and will occur when the following conditions exist:

  • When the car is moving between 20 and 55 miles per hour.
  • The throttle must be open for a minimum of 120 seconds.
  • Operating temperature above 70℃ (158℉).
  • Catalytic converter temperature above 600℃ (1112℉).
  • The evaporative emissions system is purging.
  • The code is set if the oxygen sensor voltage transitions less than 16 times from rich to lean in a 20 second interval.
  • This test utilizes two trip fault detection.

Need help with a P0159 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

Insurance Requirements for Car Registration in Kentucky
The Kentucky Transportation Cabinet requires that all drivers in Kentucky carry liability automotive insurance, or “financial responsibility” in order to operate a vehicle legally and maintain vehicle...
How to Transfer a Car Title in Idaho
In order to prove ownership of a car, you must have the title. However, when a car is sold, given away or inherited, the title needs...
P2159 OBD-II Trouble Code: Vehicle Speed Sensor B Range/Performance
Diagnostic Trouble Code (DTC): P2159 P2159 code definition Vehicle Speed Sensor B Range/Performance...


Related questions

Q: Vehicle having a hard time passing smog check.

The first thing to do would be to see what the failures are. The Check Engine light would have to be scanned to see why it is on and address the codes. Then once the light codes are fixed then...

Q: The Check Engine Light came on, I hooked it up to my scanner and got the code P0308 (cylinder #8 misfire).

An easy way to isolate if the ignition coil is the problem is to swap the #8 coil with another cylinder. Swap the #8 coil with the coil from the adjacent cylinder, then clear the codes. If the code remains...

Q: 2003 lincoln ls v6. P2270 code is read on scanner. I've changed the catalytic converter but the code is still coming back.

Hi there. The code of P2270 is coming up for an issue that is causing the emissions to be out of calibration. Check the following conditions on your engine. Check For an exhaust leak near O2 sensor For a...